Isolated right coronary artery disease is usually difficult to diagnose because of frequent negativity of standard exercise stress test. We report a case of isolated coronary artery stenosis which was not detected by standard ECG stress testing. The cardiopulmonary exercise test showed a peculiar pattern: abrupt flattening in VO2/Work relationship, plateau in O2 pulse and 90 s afterwards a plateau in heart rate, probably related to vagal afferent stimulation by ischaemia of the postero-inferior wall of the left ventricle. Multidetector computed tomography of coronary vessels and coronary angiography confirmed isolated critical stenosis of middle right coronary artery. After revascularization by PTCA, normalization of cardiopulmonary exercise test was obtained.